Admin interface for Pedestal-sp

[simongray]

Obviously gated by some kind of authorisation mechanism, e.g. a set of authorised users.

I imagine this could be a good place to keep track currently logged in users, as well as displaying some interesting metrics. This will also make it simpler to forcibly "log out" a user compared to e.g. having to SSH into a server, log in to a database, and run the query resetting the netid field in the eperson table (the current fix for SAML account mismatches on repository.clarin.dk).